I'm just about to start a two-year, part-time Certificate in Life Sciences at Birkbeck, so I thought I'd brush up with a quick potted history of chemistry. Pretty nervous as I was rubbish at science at school, but hoping to apply myself better this time (even with a baby due in 2 weeks). Enjoy!
Ancient Greek philosophers pondered the question, "how far could matter be divided?" According to Aristotle, matter was infinitely divisible, known as the “continuum theory”. However, there was a counter theory from Democritus positing the existence of discrete “atomos”, i.e. “a” (not) - “tomos” (divisible), a word that mutated in modern usage to atom. In 5th century BC, there was no evidence for either theory or philosophy, as matter could not be observed to an intelligible degree, and Aristotle’s theory held sway until the 17th century.
Anglo-Irish theologian and natural philosopher Robert Boyle (1627-1691) changed all that, and is today known as the father of modern chemistry. His most famous contribution is Boyle’s Law, an imperical observation that states:
“For a fixed amount of an ideal gas kept at a fixed temperature, P [pressure] and V [volume] are inversely proportional (while one increases, the other decreases).”
Boyle was also first to put forward the idea of an “element”, or a certain primitive unmingled body, which can be put together to form a perfectly mixed body, which we now call compounds or molecules.
Chemistry gets the oxygen of life
English clergyman and natural philosopher Joseph Priestley (1733-1804), who studied the reactions of “dephlogisticated air” (to dephlogisticate is to remove flammability) with materials, noticed the increased intensity of reactions. Today, we know “dephlogisticated air” as oxygen, i.e. air without the nitrogen, but Priestley was not the only chemist to lay claim to its discovery.
Antoine Lavoisier (1743-1794), known as one of the founding fathers of modern chemistry, deepened Priestley’s discovery by showing that oxygen was actually adding itself to the material during reactions, by calculating the mass of the material before and after the experiment. He first realised that a chemical reaction could be written down in an algebraic formula, and also isolated 19 other elements. Sadly, Lavoisier was beheaded in the French Revolution.
Another Frenchman, Joseph Proust (1754-1826), observed that when two or more elements combined to form a compound, they always combined in definite proportions by weight. This idea was developed by English school teacher and scientist John Dalton (1766-1844), who realised that all discoveries in the field of chemistry so far were better understood within the framework of Democritus’ discrete atoms, and went on to formulate his own Atomic Theory. He said (i) that each element is composed of atoms, (ii) atoms of any given element are identical, (iii) compounds form when more than one elements combine, and (iv) that elements are neither created nor destroyed.
Dalton did not perform any experiments himself, but rather came along and saw an organising principle, fulfilling the role of “synthesising” disparate ideas within a scientific field. Further substantiation for the idea of discrete atoms followed from Joseph Gay-Lussac (1778-1850) and his gas laws and Amedeo Avogadro (1776-1856) and his constant, before the statesmanship of Italian chemist Stanislao Cannizzaro (1826-1910) finally won chemistry international recognition.
Modern chemistry
Developments in the field of chemistry have advanced rapidly in the past two centuries, and one of the major breakthroughs was understanding that electrons are quantum particles that do not obey classical mechanic rules, unlike atoms and molecules. This means they have the properties of both particles and waves, so can collide with other particles and be diffracted like light.
Two observations formed the basis of modern chemistry and physics:
“The atom is not the most basic constituent of nature” - the electron was first identified by JJ Thomson (1856-1940) in an experiment using cathode rays in 1897, when he found a particle less massive than a hydrogen atom.
“Atoms have a small positively charged nucleus surrounded by electrons” - Ernest Rutherford (1871-1937) and Niels Bohr (1885-1962) worked together at the University of Manchester, and published their model of atomic structure in 1913.
Along with the publication of the periodic table in 1869 by Russian chemist Dmitri Mendeleev, these discoveries formed the foundation of modern chemistry, which became known as the “central science” given how it acted as a springboard for advances in most other scientific disciplines.
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